Jet pump surging, I've replaced everything

[glaxy1]

Hello, I need some help.

Problem: my jet pump fluctuates between 15-35psi and will not build any pressure higher than that. There is a swooshing or surging sound that continually occurs.

Location: it pulls water from a lake to supply the house. Suction Lift is 40ft, distance from foot valve to pump is 90ft.

Equipment:
brand new 2 line version of the Franklin electric rm2 jet pump

Brand new, Cage/screen, venturi and foot valve

I blocked in the discharge of the pump.
I primed the pump by using a auxiliary plug -in pump plumbed into the top suction line.
I then circulated fluid through and bled the water through a tee on the discharge line for about an hour.
When the pump is off it'll hold the pressure solid so I don't think there are any leaks on the suction line.

The pump continues to swoosh and surge though there's still air in it.

Any advice?

 

[Twowaxhack]

I’m no pump guy but sounds like a suction leak

 

[glaxy1]

Thanks for the reply, is there anything I can do to check for this? There's on a 90 fitting near the wall then it goes into the foundation. I used soapy water on the 90s, no issues.

Is there any way to test for air infiltration?

I ruled it out because the pump wasn't losing pressure but maybe I have to go back to that.

 

[Twowaxhack]

Use some shaving cream at the joints to check those.

 

[glaxy1]

Ya I checked the fittings (used soapy water) tightened up all the gear clamps. No smoking guns.

If there is an air leak it would be underground... so not much I can do with that.

I'm wondering if there is a nozzle or something I can put into the return line to over come this? Since it still gets to 40 psi... Just not consistently..

Or maybe there's some weird cavitation happening... Would getting a larger diameter impeller or having a pump running at lower speeds help?

 

[Valveman]

Like was said you have a suction leak. it will not be on the smaller drive line, but on the larger suction line. Soapy water won't do it. You are not looking for air coming out but going in instead. Foamy shaving cream will show a hole sucked in it where the leak is. Most likely at the fitting that is screwed into the pump. It looks at an angle from the picture and also needs at least two hose clamps with buckles at 180 degrees apart. No nozzle or larger impeller will fix the problem, only fixing the leak will help. Using a submersible instead of a jet pump will also solve the problem.

 

[glaxy1]

Okay thanks, I'll check the fittings and report back.

Is there any other way I could check for air infiltration? Maybe by putting pressure gauges on the two suction lines?

There's only 2 accessible fittings I can check with shaving cream...

Just trying to wrap my head around this... Would air ingress account for the pump never reaching cut off as well as the surging flow? Or just one of those.

 

[Valveman]

Yep, air is your problem. You would need a vacuum gauge on the suction line, so you can see that at higher pressure, which lowers the flow, the air makes it lose vacuum. But the vacuum gauge causes another place for a possible suction leak. Like I said, the leak is probably right where the pipe connects to the pump because the pump gets hot when it stops pumping and makes the seal at that fitting leak even more. But all a vacuum gauge will do is verify a suction leak, you are still going to need to fix the leak,